This targets the first task of #634

This package adds three executables:

1. Script for running some predefined tests, and then do the post-processing and plotting of all of them.
   Example usage: ros2 run rclcpp_performance performance_test -d output_dir [--skip]

   • output_dir: Directory where the logging files will be created.
   • -s|--skip: Don't run the tests again, only post-process and plot results.

2. communication_performance: Which logs the timestamps.
   Example usage: ros2 run communication_performance [-d output_dir] [-p publish_period_ms] [-m M][-n N][-unique] [-intra]

   • output_dir: directory where the log files will be created (it should be created before running). Default: ./logs
   • -p publish_period_ms: Publish period in ms. Default: 100ms
   • -m M: Number of messages that will be published by each publisher before exiting. Default: 1000
   • -n N: Number of publisher/subscriber pairs created. Defualt: 100.
   • -unique: If option exists, the publish method taking an unique_ptr reference is used. If not, shared_ptr publish method is used.
   • -intra: Set intra process comm.

3. posprocess_logging: Plot results.
   Example usage: ros2 run posprocess_logging -d output_dir
   Where output_dir contains the logged file.
   It plots three things:

   • The measured average publish period of each publisher.
   • The measured average publish period of each subscriber.
   • The measured latencys of each publish-subscriber pair.
     In all the cases, y axes is in ms and x axes is the result of one of the parts (one publisher, one subscriber, or one publisher-subscriber pair).

My results:
https://docs.google.com/document/d/1YRpWajYvXF_RA7nIH3Qe8RFUyVJwJoxVTSpQFJKN18U/edit?usp=sharing
Old results (841e206):
https://docs.google.com/document/d/11RBqAjcjQ4FBYkwfVtudOaHJSP_wz_TW9AGneo1_ePE/edit?usp=sharing

TODO:

• It needs a general cleaning, and add some error handling.